Parallel with the effort to extend the tillable land, everything has been done to increase the productivity of the soil under cultivation. Thanks to the application of scientific methods in agriculture and the use of fertilizer, the average yield of all crops per acre has increased since 1894 by about 35 per cent. But experts assert that owing to the excessive employment of land the soil now indicates signs of exhaustion, and that accordingly any further increase of productivity cannot be hoped for. On the contrary, the tendency will be toward a gradual decrease of productivity in the future. This is a grave forecast for Japan, and makes that country dependent more and more upon the food supply from abroad. The average yield of staple crops in Japan during the past few years comprises: barley, nine million koku (a koku is approximately five bushels); rye, seven million koku; wheat, five million koku; millet, four million koku, and rice, the most important crop, fifty-two million koku. The crops are far from being sufficient to feed a population of fifty-five millions, and Japan buys annually millions of koku of staple food from abroad. Taking rice, for instance, the average annual consumption is fifty-eight million koku, which exceeds by six million koku the average annual yield of Japan, so that the deficiency is made up by imports from Korea, China, and India. Naturally, the Japanese, being very good farmers and fond of agriculture, and yet having so small a prospect of success at home, look with eager eyes for an opportunity to cultivate land abroad. In the north there are the vast plains of Manchuria; towards the south the fertile soil of Australia; in the east, California and Hawaii appear to offer golden opportunities for industrious farmers. Manchuria, however, turned out to be too cold, and competition there with cheap Chinese labor proved unprofitable. Australia, from the beginning, never welcomed the yellow races. Only Hawaii and California seemed in all respects satisfactory for Japanese emigration. Hence, large numbers of Japanese farmers migrated to these places during the years between 1891 and 1907. Population. Another big factor of Japanese emigration is the overcrowded status of the home population. Strangely, during the three centuries of national isolation, Japan's population remained fairly static, varying only slightly around twenty-six millions. A reasonable explanation of this peculiar phenomenon may be found in the rigid social structure of feudalism, which allowed no swelling of population beyond a certain number. Malthusian factors, such as pestilence and famine, as well as artificial means of control, operated in effectively thwarting the increasing forces of population.